The main problem they encountered during production was the hair and fur, as a lot of the close ups of the camera perspective incorporated a large about of fur or hair, which is something that they had not done before. To help the movement of the hair/fur they created a groom tool, Furball, which aided the fur simulation, creating a more natural appearance to the movement. This tool was a hair shader and helped with rendering the fur, it included over 4,000,000 hair curves which was highly memory heavy, causing high render times which was a problem with ensuring if the movement of the hair/fur worked well with the final lighting and textures. The Furball render helped to create randomized clusters of hair, to further create a realistic appearance. Although the render type slowed down the production slightly, the end result worked well in the feature film.
With the Hydra model, they made a few changes to the initial model, mainly around the mouth, in which they made wider and sharper teeth as the initial model did not look menacing enough. The Hydra model was a mythical creature, in which took influence from serpents, with its scales and vertebrate, however as it is a fantasy based creation, there is room for exaggeration of its proportions and movement to make it bizarre and mythical esk.
For the textures they added a displacement to the base texture, which helped to aid extra detail and adding sub surface patterns to the scales. For the water they used just a shader with noise to try and make water, which worked really well for their first attempt. For all the textures they kept to three steps, creating the base, midtones and highlights, which helped to create a shimmer to the Hydra model, making it relate to a serpent type creature.
As most of the environment was created by the use of 3D software, the main actor was also replaced with a digital double when interacting with the CG models. For example when the main character was attacked by a wolf, the arm which the wolf had sunk its teeth into was digitally replaced so that the bite would be able to sink into the flesh more than if it had been the original arm. This was due to having the CG wolf interacting with the original arm, the arms skin needed more pull and tear from the bite, which is why the CG replacement limb helped exaggerate this action.